Jonny Brownlee admits that the Olympics have been at the back of his mind while competing in other events this year. Photograph: Anthony Upton

St Moritz has a reputation for being an alpine playground for the super-rich and famous, but while I can confirm that my morning croissants here are ridiculously expensive, I've not come to the Swiss Alps for the après-ski. Instead myself, my brother Alistair and Stuart Hayes – Team GB's three-strong men's triathlon squad for London 2012 – are here for a month of altitude training that should give us a vital edge when it comes to competing at the Games.

I'm often asked how much of a difference training at altitude makes to your body. It's a difficult one to answer because everyone is different and it affects people in different ways and to different degrees but, as a rule of thumb, an average runner, who could run 10km in 40 minutes at sea level, would probably do it in at least 50 minutes on their first day in the mountains. Yes, it's that tough.

During your first couple of minutes cantering, you think: what's all the fuss about? But then it hits you. Suddenly you are gasping for air and, if you try to fight through it, you can feel faint. It's not much easier for elite athletes. During the first week I was here, I woke up feeling awful and felt super tired doing my morning swim but now we're getting used to it. Usually it takes about eight days until your body adapts.

But when it does, you really notice the difference. Because your body uses so much less oxygen at altitude, when you get down to sea level everything is easier: your breathing is more efficient and the transfer of oxygen into your blood is more efficient too. And that leads to training sessions feeling easier and, hopefully, faster race times too.

We have been in St Moritz for more than two weeks, coming here after competing in the ITU World Triathlon Series race in Kitzbühel. I finished a decent second, behind Alistair who showed he was back to his best after his achilles injury by beating me, but perhaps the most pleasing aspect of the race was how well we worked with Stuart, who acted as our domestique for the first time.

There has been a bit of chat about whether Team GB should be using domestiques during the Games this summer but Stuart showed how valuable they can be. During the bike section we got away with a small group and pushed hard, but after that we were chased down and were soon pretty tired.

Sitting on Stuart's wheel gave us time to recover ahead of the run. Also it's nice to have another person there to keep you safe and to look out for you! On the run I felt strong but Alistair was really impressive. I pushed hard for the first lap, dropping Javier Gómez, and I was down by only three seconds at 2.5km. But when Ali extended the gap to 10 seconds after 5km I stopped trying to chase him. With the Olympics coming up there was no point trying to kill myself and risking things.

To be honest, it's been a bit strange this year because normally we try to peak for every race but because London 2012 is so massive it's always at the back of your mind. So before you go into each race you're thinking: don't crash, don't get ill, don't do anything wrong, don't get heat exhaustion and so on.

It's the first time I've experienced such feelings – normally I just go into a race and try to smash it as hard as I possibly can, whereas this year there's a small part of you that thinks: hold on a minute, the Olympics are coming up. It's a bit weird, really.

With so little time left before the race on 8 August there's not much free time to switch off. That said, we've got a cook with us in St Moritz which means we are able to watch the Tour de France and play a bit of Fifa and Call of Duty.

It's great. Food is cooked at 7.30pm every night so I just wander over. It's easy, you don't have to shop or cook so you can let your body relax and unwind after a hard day in the mountains. Sometimes we'll also hop on a ski-lift and go higher in the mountains for a stroll and a hot chocolate too. It's just a nice healthy place to be.

I know I'm a home lad, but I've not bothered taking any Yorkshire tea or many of the other trappings from England. The only thing I've brought is lots of cordial and biscuits. The cook gets everything else we need from Italy – it's just so much cheaper than Switzerland.

The plan now is to train hard for the next 10 days before coming back to the UK on 20 July, just over two weeks before the Olympics. I'll then take it easy for a few days to get over the whole altitude thing, because it takes a lot out of you, before 10 days of solid training and a taper that – touch wood – will see me spot on for the Games. Here's hoping.